\'\'\'Project Management: Critical Project Review\'\'\'

Cause For Corrective Action

Since the last submission of the project, the design team has been functioning extremely well. The only problem the group faced during this time was the addition of the PowerPoint section of the project to the original gate and group members leaving earlier than planned for the holiday. After an honest and open talk, at the November sixteenth meeting by all of the group members, a compromise was made. The compromise made was to meet several times the week after Thanksgiving as well as complete part of the project over break in order to make sure that everything was finished on time and completed to the best of the group\'s ability. The next two weeks were then planned out and occurred as the following:

November 16: future team meetings were finalized and the work to be completed over break was divided, including work on Gate 4 and revising the previous gates.

November 26: the parts of the gate finished over break were combined and uploaded followed by a discussion of the PowerPoint as well as the breakup of work for it.

November 27: combined the PowerPoint slides and finalized the presentation.

November 28: process, write up, and upload of the reassembly.

November 29: the group reviewed, corrected, and revised the gate as well as the PowerPoint. The PowerPoint was then emailed to the professor.

This design team was successful on this gate because they resolved their challenges right away with open communication as well as planned out the work that needed to be done ahead of time. Future problems, just like those previously faced by the group, will be resolved by honest, open talks along with fair compromises for each design team member. Flexibility, compromises, commitment, and teamwork are what made this team successful.

\'\'\'Product Archaeology: Product Explanation\'\'\'

Product Reassembly

After addressing the unresolved challenges and how these were overcome, Group 5 began the process of reassembling the Nerf N-Strike Longstrike CS-6. Throughout the assembly process, a camera was used to photograph each step of the process; information and observations were also recorded. The purpose of the reassembly process was to put the Nerf gun back together to its original form when the team first received the product, and then analyze the information gathered and make detailed conclusions about the product.

Reassembly Process Overview

In the next stage, Group 5 began the process of reassembling the Nerf N-Strike Longstrike CS-6. In Gate 2, the team decided that the best plan of attack was to disassemble the least complex components first and the more complex ones last. However, Group 5 decided that the most efficient way to reassemble the Nerf gun was to assemble the most complex components first and end with the assembly of the simple components. The rating scales used to determine the complexity of each component is further discussed below. The reassembly process took only one day to complete within the time span of three hours. Similar to Gate 2, the team divided the process into six phases; the reassembly of the Main Base, the Shoulder Stock, the Flip-Up Sight, the Quick-Reload Clip, the Barrel Extension, and the Final Assembly. The first hour of the process was spent assembling the Main Base, which proved to be challenging with the many small parts that had to be put into place on the component. Brianna and Sarah worked together by analyzing each individual part and, by referring to photos documented from Gate 2, were able to figure out where the proper place was for each part. The final two hours of the process were spent assembling the components in the next five phases. With the help of a screwdriver, Brian was able to attach many small parts, as well as assemble the main components. Throughout the entire process, Bryan used a digital camera to record each step as well as document every step for each phase. After three hours the team was successfully able to assemble the Nerf gun. The step by step procedure is listed below.

Ease of Reassembly

In order to safely, successfully, and efficiently reassemble the Nerf N-Strike Longstrike CS-6, each step of the assembly process was recorded. The assembly process is shown in the table along with the steps that were necessary at each phase. There were some difﬁculties associated with each process of the assembly which was predicted since each part of the Nerf gun has a different level of complexity. Group 5 divided the difficulty of reassembly into three different complexities; Connection Complexity, Force Complexity, User Complexity. Each complexity uses a rating scale ranging from one to three. Each scale is described in detail below.

\'\'\'Connection Scale:\'\'\'

The part is connected in only one place and is attached to another part by either snapping or a screw. The connection is can also be made by the parts strategic placement which holds it in place.

There are two to four connections between the parts and the connections consist of either snap tabs or screws.

There are five or more connections between parts. These connections consist of snap tabs, screws, nails or glue.

\'\'\'Force Complexity:\'\'\'

The assembly of the part requires no force and no use of a screwdriver.

The assembly of the part requires some force, as well as a screwdriver.

Once the Shoulder Stock is attached to the Base, it is difficult to take apart again.

3

Slide the Flip-Up Sight onto the top rail of the Base of the Nerf gun.

Hands

00:15

1

1

1

4

Twist the Barrel Extension onto the tip of the Base of the Nerf gun.

Hands

00:20

2

1

1

Please not for Phase 6, that the components may be assembled in order, which is not the same for the previous phases. Please see the following video, Phase 6: Final Assembly, for additional information regarding the last phase of the reassembly.

Challenges

Throughout the reassembly process Group 5 was faced with various challenges. There were three main challenges that Group 5 was faced with, which had to be addressed and solved in order to successfully complete this stage.

\'\'\'Internal Components of the Main Base :\'\'\' In the first step of Phase 1 in the assembly process, Group 5 had to insert thirteen internal components into the Main Base. This step proved to be the most challenging because of inadequate documentation of parts from the disassembly process in Gate 2. When the Main Base of the Nerf gun was disassembled many small internal components fell out of the Main Base as the two halves were being taken apart. This made it difficult for Group 5 to recall where each piece went inside of the Main Base. However, after viewing the pictures previously taken, carefully inspecting the data originally collected, and analyzing the components, including their functions, each internal component was successfully placed inside of the gun. Group 5 spent an hour of the reassembly process going through every small component and determining its proper placement inside the gun.

\'\'\'Attachment of the Air Chamber System :\'\'\' The air chamber system consists of the Internal Air Shaft Spring, Air Chamber 1, and Air Chamber 2. The insertion of this system onto the Main Base of the Nerf gun proved to be challenging when Group 5 began the reassembly process. Air Chamber 1 must fit part way inside the Internal Air Shaft; however, the Internal Air Shaft Spring must fit inside the Nozzle Divider. With the many small components already placed inside the Main Base, inserting the air chamber system required two people and careful placement so as not to disturb the components already inserted inside the gun. After inspecting pictures taken from the disassembly process, Group 5 was able to successfully insert the air chamber system onto the Main Base. This step was also challenging due to the fact that most of the grease originally found on the air chambers and spring had been rubbed off due to the handling of the components throughout the stages. The team attempted to touch the greased portions of the components as little as possible, which allowed for some of the grease to remain in tacked and also allowed for easier sliding between the chambers and the spring.

\'\'\'Assembly of Barrel Extension : \'\'\'Group 5 was faced with another challenge on the first attempt to assemble the Barrel Extension. The team attached the two Barrel Protective Covers to the Barrel Extension Base before connecting the two halves of the base together. When the two halves of the Barrel Extension were then put together, it was found that the screws that needed to be screwed into the base were blocked by the Barrel Protective Cover. All the screws then needed to be removed along with the one of the Barrel Protective Covers. It was the cover that had the holes located on the outside of the component for the screws. It was determined that the order of the assembly of the Barrel Extension is important and the design team analyzed the process. It was found that only one Barrel Extension Cover could be attached first, which was the one that had holes on the inside of the component. Next the entire Barrel Extension Base should be attachment, and finally the second Barrel Extension Cover could be assembled to the component. More in depth analysis before screwing the Barrel Extension together would have saved the design team this challenge.

Original Assembly

After the design team reassembled the Nerf N-Strike Longstrike CS-6, they analyzed the process that they took throughout the reassembly. They observed the placement of all of the components, the size of the components, and how the different components interconnected with one another. From this analysis and the firsthand experience reassembling the Nerf gun, the design team came to the conclusion that the original Nerf N-Strike Longstrike CS-6 was originally assembled by both machines and human workers before it was packaged and delivered to the customers. The design team\'s conclusion was that the small parts as well as screws in the Main Base were assembled by a machine. Human assistance was also used to maneuver certain components, such as the Trigger and Internal Spring 2 Connector, because they interconnected with one another. Human assistance, the design team concluded, was also involved when the sides of two parts needed to be closed together and often snapped in place. These parts include the Main Base, the Shoulder Stock, the Barrel Extension, and the Flip-Up Sight. The design team also concluded that machines were used to screw the screws in place used in the Shoulder Stock, the Barrel Extension, and the Flip-Up Sight. They were also used in combination with human assistance for the assembly of the Flip-Up Sight. The remaining parts of the Shoulder Stock, Barrel Extension, and Quick-Reload Clip were most likely assembled only by machines. The machines though were most likely monitored by human interaction to ensure their functionality in the assembly. The design team came to these conclusions after a great deal of analysis. These assumptions came from the idea that small parts in tightly located areas were most likely inserted by a machine, while parts that needed some maneuver or slight force were most likely accomplished through human interaction. This is most likely so that components are located in their correct places while remaining intact. The Nerf N-Strike Longstrike CS-6 is a product with a detailed assembly produced by a combination of humans and machines in order to produce a fully functioning device.

Assembly Versus Disassembly

After completing the assembly of the Longstrike CS-6, Group 5 then compared the process to the disassembly process. Both processes were found to be similar in many ways, including the use of six different phases for each process, the tools used, as well as the parts found. However, the reassembly process was found to be more difficult than the dissection. Taking each piece out of the Nerf gun proved to be a simple process, but when the team was forced to put back what they had removed, the complexity of the process increased. The challenges faced in reassembling the small parts into the Main Base along with the other challenges faced, caused the reassembly process to take an hour longer when compared to the disassembly process. Although the assembly was found to be more difficult to complete, the documentation of the process was easier and more detailed because the team knew what information needed to be recorded and what was important for the report due to prior experience from the disassembly process. For future recommendations for Group 5, more pictures as well as information needed to be recorded during the dissection of the Nerf gun to allow for an easier and precise assembly.

Mechanism

There are many mechanisms located inside the Nerf N-Strike Longstrike CS-6 that assist in the functioning of the device; however, the design team has focused on the trigger mechanism during the analysis and reassembly of the product. The purpose of this mechanism is to release Air Chamber 2 from its locked position behind the Internal Spring 1 Connector. This Trigger mechanism is considered a linear cam; in this system the Trigger is the cam, while the Internal Spring 1 Connection is the cam follower. When Air Chamber 1, Air Chamber 2, and the Internal Air Shaft Spring are pulled back by the Cocking Bolt, Air Chamber 2 and the Internal Air Shaft Spring are held in place by a plastic stopper located on the top front edge of Air Chamber 1. The Cocking Bolt is then pushed forward to its original position, moving Air Chamber 1 back to its original position as well. In order to release Air Chamber 2 and the compressed spring, the Trigger must be pulled. The Trigger is a long strip of plastic with a small inclined plane located at the center of the top surface. When the Trigger is pulled back, this incline plane pushes the Internal Spring 1 Connection upward, as illustrated in the Trigger Mechanism picture below. The spring, Internal Spring 1, connected to the Internal Spring 1 Connection allows for the cam follower to be pushed upward and for the part to remain in its proper location in the Main Base of the Nerf gun. As those two parts are pushed upward, Air Chamber 2 and the Internal Air Shaft Spring are released, causing air to be forced through Air Chamber 1. This then forces the foam dart from its stationary position in the tube. The equations involved in the design of the mechanism include (1): F=ma and (2): F=(-k(x)). When the Trigger is pulled, it applies a force on the Internal Spring 1 Connection, and this force can be calculated using the first equation. A force is also applied between the Internal Spring 1 Connection and the Internal Spring 1 which can be calculated using both equations. Also, both force equations can be used to determine the force between Internal Spring 1 Connector, Air Chamber 2, and the Internal Air Shaft Spring. This linear cam mechanism with the Trigger and Internal Spring 1 Connection is essential in the functioning of the Nerf gun, without which, would not eject the bundle of kinetic energy.

\'\'\'Trigger Mechanism :\'\'\' When the Trigger (Cam) is pulled back, the Internal Spring 1 Connection (Cam Follower) is pushed upward by the incline plane. This is shown with the arrows in the picture.

Design Revisions

As the design team members assessed, disassembled, analyzed, and then reassembled the Nerf N-Strike Longstrike CS-6, they were able to fully understand the functionality and reasoning behind the design of the Nerf gun. From here, they were able to work together to recommend three design revisions to the original Nerf gun in order to improve a specific quality of the gun as well as address global, societal, economic, and/ or environment concerns. The following three redesigns of the Nerf gun are system level changes that have the potential to increase the desirability of the Nerf gun.

\'\'\'Crank N-Nerf :\'\'\'

This first redesign is a mechanism change of the Nerf N-Strike Longstrike CS-6. It removes the linear cam system involved with the Cocking Bolt and replaces it with a rack and pinion system. For this system revision, the Cocking Bolt would be replaced with a hand crank connected to a gear inside of the Nerf gun. This gear would then mesh with the gears located on the bottom of a sliding piece of plastic that is added which will connect to Air Chamber Two. This can be seen below in the Crank N-Nerf figure which shows a solid model of the new mechanism to the Nerf gun. [Note: It is colored orange simply for viewing sake.] This mechanism change would then alter the way the Nerf gun is used. Instead of pulling the Cocking Bolt back until it is locked in place and then forward again, the hand crank would be turned to the user’s desired amount, up to a specific maximum, as the gears mesh during the rotation of the crank. Then the dart would be released just as before by pressing the Trigger. The Trigger would still use a linear cam system as before, but with a slightly altered design to lock Air Chamber Two in place at different distances as it is cranked back as well as allow for it to be pushed forward when the Trigger is pressed. Air Chamber Two would also have an added stopper on the bottom surface to catch along the Trigger. The crank will also be rotated back into place as the Trigger is pulled. The highlight of this new design is that it will allow for a variety of range values of the dart depending on the amount of rotation of the crank as well as the potential for longer ranges as stronger spring constants should be able to be used with this new mechanism, though further testing as well as analysis is needed. Not only will this revision increase the performance of the Nerf gun, but it also has a societal factor, increasing the safety of the gun to the user as well. Before, with the Cocking Bolt, a child could easily pinch their fingers in the slots on the side of the Main Base where the Cocking Bolt was moved manual backward or forward. With this new design, there will be no chance of pinched fingers as the crank will be located at a safe distance away from the Main Base and all of the other parts will be concealed inside the Main Base of the gun. This redesign will also decrease the realistic factor of the Nerf gun which is a global concern, especially with the U.S. law that was put into place in May of 1989 that stated that "no person shall manufacture, enter into commerce, ship, transport, or receive any toy, look-alike, or imitation firearm" [1]. This redesign will resemble an actual gun even less than it does now. This will allow the Nerf gun to be more acceptable in countries throughout the world, especially with the recent violence and terrorism going on. Finally, this revision will only cause a slight increase in the cost, if any. Injection molding will be used to create the new plastic parts, which is an economical process for large scale runs. Further research would be needed for exact cost projections but economically this redesign should not change the cost of the Nerf gun to the customer as a result of the new parts. This mechanism revision will cause the existing Nerf gun to be changed into a unique design unlike any current solutions today. This will then in turn increase the market or target audience for the Nerf gun. The Crank N-Nerf is a Nerf gun with longer, adjustable, and safer ranges for children and adults to play with.

\'\'\'Crank N-Nerf : \'\'\' This picture shows the new design mechanism used to ready the Nerf gun. It replaced the previous Cocking Bolt linear cam system with a rack and pinion crank system.

\'\'\'Nerf Semi-Automatic :\'\'\'

The second design revision changes the single shot Nerf gun into a semi-automatic. The current model of the Nerf N-Strike Longstrike CS-6 is equipped with a Quick-Reload Clip that holds six foam darts. After the clip is attached to the gun, the Cocking Bolt is pulled back, which pushes a dart into Air Chamber One where the bullet rests until the trigger is pulled. The Cocking Bolt is then pushed forward where it stays until the dart is released. For this system, only one dart can be loaded at a time into Air Chamber One and the Cocking Bolt must be pulled back and then forward between each shot, reloading only one dart into the Nerf gun. The design team’s revision however alters this system level single shooting of the Nerf gun. This redesign is the addition of a revolving chamber to the firing system of the Nerf gun, as shown below in the Revolving Chamber picture. [Note: It is colored orange simply for viewing sake.] By adding a revolving chamber, the same quantity of darts are at the user’s disposal; however, the revolving chamber will create a semi-automatic firing system. The user will no longer have to cock the gun back and then forward before each shot, but instead, the Nerf gun will only need to be loaded once with darts and then after each shot, the chamber of darts will automatically rotate allowing the gun to be ready to shoot. This chamber system will be lowered out of the Main Base to loaded and then fully enclosed in the Main Base during usage. For this system to be created the Cocking Bolt must be removed and the air chamber and piston system must be altered to allow for the automatic loading of the dart after each rotation of the chamber. The piston system must then be pulled pack and released automatically each time the trigger is pulled. This design revision will therefore impact the usage and performance of the Nerf gun. It also affects various economic and societal concerns. By adding the revolving chamber, the Nerf N-Strike Longstrike CS-6 will be able to shoot darts semi-automatically creating a unique Nerf gun. This Nerf gun not only has a new firing mechanism, but since the original barrel design was not changed, it also has a long firing range. The combination of these two factors will increase the desirability of the product as well as have the potential to expand its target audience. By adding a surprise addition, such as the revolving chamber, customer satisfaction increases which then increases sales as well as the company’s profits affecting economic concerns. Societal concerns are also addressed by this design revision. In the original design of the Nerf N-Strike Longstrike CS-6, the Cocking Bolt had slots on the side of the Main Base where it was manually pulled backward or forward, which caused a potential safety hazard as a child’s small fingers could easily be pinched in these slots. With this redesign however, these components are eliminated and the automatic cocking of the Nerf gun will take place inside of the Main Base of the gun as well the automatic rotation of the chamber. This greatly increases the safety of the Nerf gun to its users and the people who come into contact with the Nerf gun. This design revision, creating the Nerf Semi-Automatic, is a unique Nerf gun that takes firing and distance to new level for both children and adults.

\'\'\'Revolving Chamber : \'\'\'This solid modeling picture shows the revolving chamber that would be added to the Nerf gun. The picture on the left is the solid model, while its part drawing is on the right.

\'\'\'Bow & Dart Nerf :\'\'\'

The third and final recommended design revision by the design team is one that changes the way in which the force is applied to cock the Nerf gun. Currently the Nerf N-Strike Longstrike CS-6 is cocked by manually pulling the Cocking Bolt back until it locks into place and then pushing it back forward again. The dart is then released once the trigger is pressed and Air Chambers Two is pushed back to its original position. This new design, however, removes the Shoulder Stock, the Cocking Bolt, and the Trigger from the original design. It also changes the slots on the sides of the Main Base to be located on the top and the bottom. Then a new component is added to the design, a bow. The bow is half plastic on one side and half rubber band on the other. The plastic half of the bow is attached to the top and bottom of Air Chamber Two as well as come out of the slots on the top and bottom of the Main Base. The two ends of the plastic section of the bow are then connected with specific rubber band along the outside back-end of the Nerf gun. A drawing of this can be seen in the Bow & Dart Nerf picture below. This redesign of the Nerf gun then changes how the gun is used. Instead of cocking the Cocking Bolt back and then forward, now with one hand holding the Quick-Reload Clip, the other hand pulls the rubber band back. By pulling the rubber band back, the plastic it is connected to moves back along the slot lines, and so does Air Chamber Two, which the plastic part of the Bow is attached to. This allows the user to then pull back the rubber band as far as they desire, aim, and then release the rubber band while still holding the Quick-Reload Clip. When the rubber band is released, it has the same effect as pulling the Trigger. The dart is pushed out of the Nerf gun and Air Chamber Two, along with the Bow, is pushed back to its original starting place. The reasoning behind this new design revision to the existing Nerf gun is due to specific consideration of materials. Since this new design eliminates many parts and only adds one, the materials used in the revision decrease. This will influence environmental concerns as less material is being used during the life-cycle of this new design. Also, an economic factor as a result of less material being used is that the cost of the Nerf gun will be less than before. This unique Nerf gun along with its ability to change its range will also increase desirability of the product as well as have the potential to increase its target audience. Finally, this design revision has the potential to support stronger spring constants which would increase the range of this product as well as increase its desirability even more. The Bow & Dart Nerf combines the traditional Nerf gun with a bow and arrow idea to create a redesign that is profitable and enjoyable to the targeted audience of children as well as adults.

\'\'\'Bow & Dart Nerf :\'\'\' The left section shows the original Nerf N-Strike Longstrike CS-6 with its Trigger, Shoulder Stock, Main Base, Barrel Extension, Cocking Bolt, Slots, Quick-Reload Clip, and Dart. On the other side, the third redesign of the Bow & Dart Nerf is shown. It has a Main Base, Barrel Extension, Bow, Quick-Reload Clip, and Dart.